What a mess

This 99 XP has been a nightmare from the start. I knew it needed work when I bought it, but wasn't expecting this. First the crank was trashed so I had to rebuild it. Then the carbs were so dirty and corroded that I could not even get them apart, let alone clean them. So I had to buy a new/used set. Then the jet pump bearings were bad, but not only that but the shaft was rusted onto the impeller. To the point no amount heat or anything was getting it apart, I broke my bench vise trying. So I had to get a new/used jet pump housing.
So now it's all back together woohoo I get to ride it. I'm on it ten minutes just putting around taking it easy, and boom I roll the stupid thing. Luckily I was rite next to the dock, I load it up get it home and make sure the motor Didn't any water in. So now I get it out again yesterday and again just taking it easy. Went full throttle for a couple seconds, but nothin crazy. Next thing I know motor starts running like poop and dies. Won't turn over I'm getting the big old middle finger. Mind you I'm 2 miles from the dock. Not sure what made me madder that fact that the ski died or 4 boaters drive rite by me and never stopped. Luckily I had a mini oar with me.
So I take the motor apart today and find total annihilation. The bad cylinder had oil in it no scuffing or gouging on cylinder wall or piston (what's left of it) but from the carnage it looks as if the bearing had no oil to it.
I'm so disgusted with this ski I'm ready to take 30 pounds of tannerite to it and watch it explode.

Did you do pistons and a bore, or hone when you did the crank? You said you rebuilt the crank? I hope you mean you bought a rebuilt crank. When you buy one in that condition, you have to go through everything. Complete fuel system, driveline, motor and electronics. Even if an old ski like that is given away, sometimes its still not worth rebuilding. After they sit for so long, they need so much work that unless you have the parts on a shelf, the ski isn't worth what you'll have to put into it.

It looks like you have a nice crack in the cases now. It might be time to cut your losses. Best of luck if you decide to build it. 951s can be reliable engines when built right and cared for.

If you question the oil pump, I'd go premix when rebuilding it. Were you running double oil for the break in?